Thanks!, But I don't understand this part. What's the difference between transferring your own Pokémon (not possible) and trading with a friend (possible)? Is it some new feature in gen 5 or something?

Sorry about the spam message above here. It was a test message and I thought it didn't post because the site server was slow, else I would've edited it with the message I posted just now.

When I say transferring your own Pokémon, I mean the whole migration/import-your-past-gen-Pokémon thing. xD The only reason why you're unable to do it right now is because, well, you haven't completed the main story yet, so you're unable to get to the PokéTransfer Lab since the route it's on is right now inaccessible to you.

You can simply get around this if you have a friend that did go through the main story, since that friend will be able to access the PokéTransfer Lab, migrate your Pokémon for you, and then trade it over to your game without any limitations.